We present first estimates of rates of non-take-up for social assistance in Germany after the implementation of major social policy reforms in 2005. The analysis is based on a microsimulation model, which includes a detailed description of the German social assistance programme. Our findings suggest a moderate decrease in non-take-up compared to estimates before the reform. In order to identify the determinants of claiming social assistance, we estimate a model of take-up behaviour which considers potential endogeneity of the benefit level. The estimations reveal that the degree of needs, measured as the social assistance benefit level a household is eligible for, and the expected duration of eligibility are the key determinants of the take-up decision, while costs of claiming seem to play a minor role.